Reflector



April 14, 1931- w. A. DUNLAP 1,800,886

REFLECTOR Filed Feb. 23, 1929 3 Sheets-Sheet l INVENTOR Add NW ZMM Mi I Aprifi M, W. A DUNLAP REFLECTOR Filed Feb. 25, 1929 5 Sheets-$heet 5 INVENTOR Patented Apr. 14, 1931 UNITED STATES PATENT; OFFICE WILLIAM. A. DUNLAIP, OI PITTSBURGH, IIIDTBYLVANIA BEI'LEGTOB Application filed February 28, 1929. Serial Io. 841,983.

My invention is an improvement in replaced'side by side, their focal centers not bellectors especially designed for illumination ing central with the center of the reflector, sit a definite area, in either single or multiple distorted distribution of light results, estione, peciallywhen one of the light sources ceases It is especially designed for illuminating to function. 58 the prescribed area or areas of a vertical sur- In order to overcome these objections I face, such as a bill board or the like. ,Such have designed m reflector so that the direct boards are usually rectangular, of various and reflected lig t rays from either one or dimensions, and for the best results, should two hght sources are concentrated within 1 be evenly lighted all over, with proper and restricted areas, and so directed as to cause equal distribution and without waste of light equal distribution of allthe li ht emitted. rays either beyond the surface, orby dupli- Referring to the drawings s owing certain cation as by overlapping from one section or preferred embodiments of the invention:

t an dj gj e fg =;T Flg. 1 is a face view of a single lamp reit There aremanydesi so! reflectors made flector; i

for sign and bill boa lighting, butin'de-f F1 2 is a vertical section on the line signing most of these the important factor of II- I of Fig. 1; th lstribution of light from the light Fig. 3 is a transverse section on the sloping source in such a manner as to produce equal llne III-III of Fi 2; 20 intensity of light over the entire surface tobe Fig. 4 is a face view of a double light relighted, without undue loss of light, is not flector, s1milar to Fig. 1; sufficiently emphasized, or often neglected. J F1 5 is a vertical section on the broken This important factor is essential for corlme -V of Fig. 4, the lamp being shown in rent economical lighting, but is diflicult to elevation- T735 accomplish, as in most cases the light sources, Fi 6 1s a transverse section on the slop employed to illuminate the sign or billboard, ing hne VI--VI of Fig. 5 similar to Fig. 3.- are hung or installed approximately on a line The reflector is formed in such a manner horizontal with the top of the sign, which rethat the walls forming the sides, bottom, and suits in a shorter distance from the li ht rear portions, are sections of true parabolas 1 center to the top of the sign than the ishaving'their foci in the center of the light Lance from the light center to the base or source, with a top or upper wall providing a bottom of the sign, thereby causing the light straight or flat portion. rest upon the lower part of the sign to be Accordin to my im roved construction, weaker or less than that which is cast upon the that part 0 the li ht ux emanating from 35 upper portion of the sign. the li ht source, 0t er than that which pro- Another serious defect in most designs of jects 'rectly on the surface to be illuminated, reflectors is that the distribution of direct impinges on the several parabolic sections, and reflected light is so wide spread as to and is reflected in lines parallel to the major cause a serious loss of light by extending beaxes of the parabolas upon which they tall yond or overlapping the surface to be illuand upon the upper or strai ht side inclined ininated. at a given angle or slope. 0th the axes of One other serious defect is, that in those the various parabolas and the angle of the uplocalities where the erection, constriihtium: er flat side are so designed that the light reand maintenance of signs involve a consider- Eected from their surfaces is directed to those aoie financial outlay, it is almost imperative parts of the sign which ordinarily receive the that the surface be illuminated without inlesser or weaker light, thereby producing an terruption. In order to produce such conequal illumination over the entire surface. tinuous source other reflectors have been The sides, top, and bottom of my reflector designed having two light sources instead of are extended outwardly from the 11 ht source one, but as these two light sources are usually to such a. point as to intercept the meet and m reflected light rays in such a manner as to nate 10$ of light from overlapping. Referring to the drawings showing the single lamp form, the lower portion of the casing providing the reflector proper is provided with .an upwardly extending shell 2 having a socket 3 for insertion of the lamp 4 in the usual way.

The reflector is supported outwardly in front of a bill board or the like by a supporting arm 5 of suitable 1e h, in dotted lines, which may conveniently e in the form of a pipe or tube, coupled with the socket 3 and providing a conduit for the circuit wiring, as in common practice.

The top wall or upper portion of the entire reflecting shell surrounding the lamp 4 consists of a flat section 6 extending forwardly and slightly downwardly from. the socket shell 2, flaring or widening laterally at each side as at 7 and merging into the annular surrounding rim by a strai ht horizontal edge 8.

The rear middle portion of the shell immediately behind the lamp bulb c0nsists of a part circular parabolic reflecting section 'a, merging into and attached to the annular bottom of shell 2, arched around the lamp, and having a connecting juncture with the lower and each side reflector wall as shown.

The lower reflecting section or wall b is of arabolic form longitudinally extending rom its juncture 9 with section a downwardly and forwardly, widening towards the front and merging into the annular surrounding rim by a downwardly curved edge 10, corres nding to the cross sectional curvature of t 0 wall 6.

The side reflecting sections a and d likewise are of parabolic form longitudinally, extending from their juncture 9 with section a forwardly, downwardly and laterally at each side, corresponding to the flaring or widening degree of extension of walls 6 and 6.

Sides 0 and d join the straight edges of upper section 6 at juncture 7, bowing outwardly on a transverse plane with correspondin interior concavity, and are brought into joined connection at juncture 11 with the flaring side edge boundaries of lower section b, as in Fig. 1. v,

The side sections a and (1 also widen continuously towards the front and merge into the annular surrounding rim by the outwardly curved edge portions 12, corresponding to the cross sectional curvature of the walls a and d.

The front ed portion of the entire reflector unit is pre erably beaded or rounded as with the focal center of the lamp 4 and approximates both vertically and laterally of the reflector a median line, conforming to the plane of section II-II of Fig. 1 and to a sloping transverse plane y-y coincident with the line III, III, in the general direction of upper wall 6. Each of such planes emerge through the front sloping plane of the open end of the reflector at about the point m, Fig. 1.

Incidentally, such central line III, III, of the entire aggregate beam of emitted light impinges upon and corresponds to a central point in the area to be lighted, and effects a concentration of light within a limited area concentric with such central line which coincides with the focal center of the lamp or light source. Such line therefore, in my improved reflector, is the central axis of the desirable increased light intensity required in such prescribed area to overcome or neutralize undesirable greater intensities of those areas lyingimmediately outside of the prescribed .zone of my reflector, which are otherwise present.

Such undesirable increased intensity is ordinarily due to overlappin of outside rays or to imp ngement upon similar areas of light in connection with the use of lural units of other constructions in which t e entire beam is not similarly confined or restricted.

This latter serious'objection, with the accompanying variation in continuous illumination of an entire area by a plurality of units, with its resulting inefliciency and waste, is avoided by the use of the several parabolic reflecting surfaces 0, b, c, d and 6, in their assembled relationship to each other and to the light source.

It will be observed that the front beam emission opening of the reflector in general outline approximates a rectangle, with a straight upper horizontal boundary, the bottom and sides being somewhat concaved due to the parabolic form and transverse curvature of these walls.

Also that the said parabolic walls b, a and (1 merge into each other and into the .rear parabolic wall a almost continuously,

i. e., at the very obtuse junctures 11 and 9 whereby the several interior reflecting wall surfaces are practically continuous.

The only juncture of pronounced angularity is between the lateral boundaries of upper wall 6 and the upper boundaries of side walls 0 and d, at 7.

In designing my improved reflector I have so disposed these several reflecting surfaces as to utilize to the best advantage the angles of incidence and reflection according to the well known law.

Direct rays from the source of light outwardly are emitted within the several edge boundaries 8, 12, 12 and 10 for illumination of a corresponding enlarged area on the i1- laminated surface, dependent on its distance.

Reflected rays a from reflector a extend in parallelism forwardly and downwardly through the lower middle portion of the emission openin as a composite beam against a correspon ing interior section or area of the whole area being illuminated.

Reflected rays 6 from the entire divergin surface of upper reflector wall 6 are reflected downwardly and laterally at each side within the confining limits of upper edge 8 and side edges 12 in the form of a composite ex anding beam. Such beam will be distri uted evenly over the entire illuminated area, contributing its proportion of illumination thereto equally throughout the prescribed area.

Reflected rays 6' from the entire diverging surface of lower reflecting wall I) are reflected horizont lly and laterally at each side within the confining limits of the upper and side edges in the form of a composite expanding horizontal beam.

Such beam will be distributed evenly over the upper full width portion of the illuminated area, contributing its proportion of illumination thereto equally throughout such prescribed area.

Reflected rays 0' from the entire diverging surface..of side reflecting wall 0 are re flected-laterally towards the opposite side and downwardly in the form of a vertically expanding composite beam. Such beam will be distributed evenly over the full depth of one side portion of the illuminated area, contributing its proportion of illumination thereto equally throughout such prescribed area.

Likewise rays d" from the entire diverging surface of the opposite side reflecting wall at are reflected laterally towards the opposite side and downwardly in the form of a vertically expand ng composite beam. Such beam will be (llS\.ll)11td evenly over the full depth of the other side portion of the illuminated area, contributing its proportion of illumination thereto equally throughout such prescribed area.

The total effect of such disposition of the light, combining both direct and reflected rays, is to project upon the prescribed area a composite beam of direct and reflected rays having prescribed boundaries generally con forming to the outline of the emission 0 ening of the reflector, and of a substantially constant value throughout.

This is because the direct rays from the lamp are themselves limited by the edges surrounding the opening in advance of the lamp, while the several beams composed of the rays reflected from the several parabolic surfaces and the top flat surface are so disposed as to be equally distributed and equally supplement such direct rays, giving a general average increase of illumination over the whole area.

Figs. 4, 5 and 6 show a modified construction of reflector utilizing a pair of lamps 4a arranged side by side in sockets 3a within a common laterally elongated shell 2a, above a double construction reflector. Such double reflector is in all respects generally similar to the single reflector above described except that the lower parabolic reflecting surfaces 62 are joined at a middle median line 13. The top wall 6a and the side walls 02 and d2 are substantially the same as already described, extending forwardly to the common transverse plane of the front emission opening surrounded by a terminal edge or bead 8a, 12a, 10a, forming a continuous terminal edge.

Each such side construction, including the enclosing walls and their reflecting surfaces meeting at 13, as to the surfaces til-02 and b2-d2 respectively, merge backwardly into the rear reflecting walls a2, combine with said walls and with the shell 2a in the same manner above described.

In such double form of reflectorshaving two sources of light the rear parabolic sections a2 are slightly inclined so that their axes converge to a point on the surface of the sign or other illuminated area, thereby eliminating distortion of light should either lamp be extinguished, as at a, Fig. 6.

In such double arrangement the combined direct rays of the twin lamps 4a are pro jected outwardly, laterally and downwardly, with direct impact against the area to be illuminated, in an enlarged outline of equal light value corresponding to the outline of the surrounding edge opening of the reflector.

The reflected rays from the inner surface of the flat upper wall 6a are projected downwardly and forwardly as indicated at 6 in the same manner as has been described as to the single construction; the reflected rays b are reflected forwardly from the surface of lower walls 62; the-reflected rays from each surface of side walls 02 and d2 are reflected laterally toward the opposite side of the surface area as indicated at c", and the reflected rays from the inner surface of opposite parabolic surface of wall d2 are projected inthe opposition direction in the same manner.

The composite beam composed of rays a" are reflected in parallelism in the form of double beams forwardly and downwardly from the reflecting surface of rear wall a2 behind the source of light in the same manner already described, with slight convergence inwardly as described.

The relative proportions of the reflecting surfaces, in such double construction, may be slightly varied, as by extending the rear walls 62, c2 and d2 upwardly at the rear walls (12, as indicated at 9 in Fig. 5.

Such disposition slightly reduces the value reflecting value of the lower walls 122 and side walls 02-d2, but without disturbance of the general a gregate effect, and with a resulting general l average of illumination over the entire area.

The construction and utility of the reflector, either in single or double form, will be readily understood and appreciated from the foregoing description. lVhen used as a single reflector orunit, a prescribed area of limited dimensions may be fully, evenly and completely illuminated from top to bottom or from side to side, within the limitations of the complete prescribed emitted beam.

On the other hand, a series of such individual units or reflectors may be arranged outwardly in front of and alon the upper portion of a sign board or the li e, properly spaced apart to avoid undue overlapping of t e sides of the several main beams, with an equally complete general average of illumination throughout the whole area to be lighted.

It will be understood, of course, that the individual units may be made in various sizes or dimensions, dependent on the size and 1 power of the source of light elements, or variously changed or modified in construction or other respects by the skilled mechanic, but that all such changes or modifications are to be understood as within the scope of the following claims.

What I claim is:

1. A reflector composed of a series of'lamp enclosing walls providing an upper downwardly and forwardly sloping surface, a lower downwardly and forwardly sloplng surface, and opposite side surfaces having a parabolic curvature diverging laterally and downwardly and merging into said upper and lower surfaces.

2. A reflector composed of a series of lamp enclosing walls providing an upper downwardly and forwardly sloping surface, a lower downwardly and forwardly sloping surface, and opposite side surfaces diverging laterally and downwardly and merging into said upper and lower surfaces, each of said lower and side surfaces having a parabolic curvature.

3. A reflector composed of a series of lamp enclosing walls providing an upper downwardly and forwardly sloping surface, a

lower downwardly and forwardly sloping surface, and opposite side surfaces of parabolic curvature diverging laterally and downwardly and merging into said upper and lower surfaces, said lower surface extending in concave parabolic curvature formation divergently around and away from a focal center. g V

4. A reflector composed of a series of lamp enclosing walls providing an upper downwardly and forwardly sloping surface, a lower downwardly and forwardly slopin surface, a rear concave reflecting surface, an opposite side surfaces having a parabolic curvature diverging 'laterall and downwardly and merging into sai upper, lower and rear reflecting surfaces.

5. A reflector consisting of a lamp receiving casing having a lamp socket, an upper flat forwardly extending wall and a rear concave wall connected with said casing, and a bottom and opposite concave side walls each having a parabolic curvature and joined to each other and to the upper flat and rear concave walls respectively.

6. A reflector composed of a series of lamp enclosing walls providing an upper downwardly and forwardly sloping surface, a lower downwardly and forwardly sloping surface, and opposite side surfaces diverging laterally and downwardly and mergin into said upper and lower'surfaces, each 0 said lower and side surfaces being concave and having a parabolic curvature providing a reflecting surface ofconstantly increasing distance from an enclosed source of light.

7. A reflector consisting of a lamp receiving casing having a lamp socket, an upper flat forwardly extending wall and a rear concave wall connected with said casing, and a bottom and opposite concave side walls joined to each other and to the upper flat and rear concave walls respectively, said concave walls being of parabohc form in a direction away from a lamp mounted in the socket.

8. In a reflector as described, a socket casing provided with a lamp socket, an upper front reflecting wall connected with the front of the socket casing and extending downwardly and forwardly therefrom, a rear concave reflecting wall connected with the rear of the socket casing and extending downwardly and rearwardly therefrom, opposite concave parabolic side reflecting walls connected with the upper wall and the sides of the rear concave wall diverging laterally and downwardly therefrom, and a lower concave parabolic reflecting wall connected with the bottom of the rear concave wall and with the side walls, the upper, side and lower walls terminating in a continuous surrounding edge on a common transverse plane.

9. In a reflector as described, a 'socket casing provided with a lamp socket, an upper front reflecting wall connected with the front of the socket casing and extending downwardly and forwardly therefrom, a rear concave reflecting wall connected with the rear of the socket casing and extending downwardly and rearwardly therefrom, opposite concave parabolic side reflecting walls consocket.

10. In a reflector as described, a socket casing provided with a lamp socket, an

11 h front reflecting wall connected with the fl ont ofthe socket casing and extending downwardly and forwardly therefrom, a rear concave reflecting wall connected with the rear of the socket casing and extending downwardly and rearwardly therefrom, o posite concave side parabolic reflecting w s connected with the upper wall and the sides of the rear concave wall divergin laterally and downwardly therefrom, an a lower concave arabolic reflecting wall connected with the ttom of the rear concave wall and with the side walls, each of said rear, side and lower walls extending in concave formation dicenter 0 a lamp mounted in each socket.

In testimon whereof I aflix my si ature.

' y WILLIAMA. DUfiAP.

vergentl around and away from the focal center 0 a lamp mounted in the socket.

111. In a reflector as described, an elongated socket casing provided with a air of side by side lamp sockets, an upper ront reflecting wall connected with the front of the socket casin and extending downwardly and forwardly t erefrom, a pair of side by side rear concave reflecting walls connected with the rear of the socket casing and extending downwardly and rearwardly therefrom, opposite concave side reflectin walls connected with the upper wall and t e outer sides of the rear concave walls diverging laterally and downwardl therefrom, and a pair of lower concave re ectin walls connected together at the middle an to the rear concave walls and at opposite sides to the side walls, the upper, side and lower walls terminating in a continuous surrounding edge on a common transverse plane.

12. In a reflector as described, an elongated socket casing provided with a pair of side by side lamp sockets, an upper front reflecting wall connected with the front of the socket casing and extending downwardly and forwardly therefrom, a pair of side by side rear concave reflecting walls connected with the rear of the socket casing and extending downwardly and rearwardly therefrom, opposite concave side reflecting walls connected with the upper wall and the outer sides of the rear concave walls diverging laterally and downwardly therefrom, and a pair of lower concave reflecting walls connected together at the middle and to the rear concave walls and at opposite sides tothe side walls, the upper, side and lower walls terminating in a continuo'us surrounding edge on a common transaround and away from the focal 

